Known in the art is a mill for hot rolling of bevel gears (cf., for example, USSR Inventor's Certificate No. 753,521 Cl. B 21 H 5/04, 1977), comprising a stand, a gear blank spindle rotatably mounted in the stand, a tool spindle rotatably mounted in the stand so that it can move transversely to the axis of the gear blank spindle.
The mill is also provided with a device for heating the gear blank, which comprise a platform mounted for parallel and perpendicular movement relative to the axis of the gear blank spindle under the action of hydraulic cylinders, a transformer and a high frequency current inductor mounted on the platform. Mounted in the gear blank spindle is a device for clamping the gear blank.
One of the important conditions for successful rolling of bevel gears is stable and uniform heating of the gear blank being treated prior to the rolling operation. To ensure stable and uniform heating of the gear blank, it is necessary that a gap of a preset size be maintained between the gear blank and the h.f. current inductor incorporated in the gear blank heating device. The gear blank used is a forged stock machined over datum surfaces, that is, over its end and central opening. In the given case, the gap between the gear blank and the h.f. current inductor remains permanent owing to the dimensional accuracy of the datum surfaces. However, preliminary machining of the datum surfaces of the gear blank brings down the economic efficiency of the mill by reason of the waste of metal unavoidably lost in shavings during machining.
There is also known a mill for hot rolling of bevel gears (cf. for example, USSR Inventor's Certificate No. 925,501 Cl. B21 H 5/04, 1980), which comprises a stand, a gear blank spindle mounted rotatably in the stand, a tool spindle mounted in the stand with the possibility to rotate and move at an angle to the gear blank spindle. The mill is also provided with a gear blank heating device which includes a platform capable of moving in parallel with and transversely to the axis of the gear blank spindle by means of hydraulic cylinders, a transformer and a h.f. current inductor mounted on the platform. Placed in the gear blank spindle is a gear blank clamping device having a chuck and a hydraulic cylinder. The clamping device interacts with a stop member provided to limit the movement of the h.f. current inductor when travelling in parallel with the axis of the gear blank spindle in the direction of the gear blank. Thus, the stop member is used in the known mill for maintaining the gap of a preset size between the gear blank and the h.f. current inductor irrespective of the height of the gear blank portion being clamped, which may vary in the hot-forged blanks over the range of several millimeters.
The prior-art mill for hot rolling of bevel gears makes it possible to hot roll bevel gear blanks in as-forged condition without premachining of datum surfaces.
However, in the above-described mill for hot rolling of bevel gears the stop member is cantilivered directly on the h.f. current inductor and interacts during heating with the chuck of the clamping device, rotating together with the gear blank. With such arrangement of the stop member, the platform mounting the gear blank heating device is subjected to the action of the bending moment, while the stop member wear increases because of its friction with the rotating chuck incorporated in the gear blank clamping device. By reason of unfavorable operating conditions, the stop member and the h.f. current inductor very soon become unserviceable, the stability of heating of gear blanks is upset, and the operating reliability of the mill for hot rolling of bevel gears is impared.